VENICE, ITALY - As Venice prepares to host its famous carnival next month, the lagoon city's inhabitants have more than masked balls and black-tie parties on their minds.

The architectural gem known historically as La Serenissima — the Most Serene — is slowly slipping beneath the waves.

Rising sea levels and subsidence, resulting from decades of groundwater extraction for agriculture and industry on the Italian mainland, have caused Venice to sink 23 centimeters in the past century. Its Renaissance palaces, historic churches, and stone bridges are now menaced by floods more than 50 times a year.

ADVERTISEMENT

Last month, the worst flooding in 22 years caused the lagoon to rise more than 5 feet above normal, forcing tourists to bunker down in hotels and shopkeepers to put up sandbag barricades. One wakeboarder streaked across the waters that swamped St. Mark's Square.

It also rekindled controversy over a multimillion-dollar scheme to save Venice's art and architecture. Known as Project Moses, it entails the construction of 78 giant steel gates across the three inlets through which water from the Adriatic flows into Venice's lagoon.

The hinged panels, 92-feet wide and 65-feet high, will be fixed to concrete bases being dug into the sea bed. When a dangerously high tide is predicted, compressed air will be pumped into the hollow panels, forcing them to rise on their hinges, forming a barrier to the waves.

Project Moses is both an allusion to Moses parting the waves of the Red Sea and a neat acronym for the project's name, Modulo Sperimentale Elettromeccanico.

It was inaugurated by Prime Minister Silvio Berlusconi in 2003 and is now expected to be operational in 2014.

But it has been dogged by political feuding, environmental concerns, accusations of political cronyism, and unease over its price tag: $4.5 billion, with estimated annual maintenance costs of $11.5 million.